#include <stdio.h>

void to_binary(unsigned long n);

int main(void)
{
  unsigned long number;
  printf("Enter an integer (q to quit):\n");
  while(scanf("%ul",&number) == 1)
  {
    printf("Binary equivalent: ");
    to_binary(number);
    putchar('\n');
    printf("Enter an integer (q to quit):\n");
  }
  printf("Done.\n");
  return 0;
}

void to_binary(unsigned long n)
{
  int r;
  r = n%2;
  if(n>=2)
    to_binary(n/2);
  putchar('0' + r);
  return ;
}
